It is known that the accessory belt drive for hybrid electric vehicles may include a belt driven starter/generator. For such a system special belt tensioning is provided to satisfy both modes of operation: starting and generating. In prior art systems two tensioners can be used, for example, a hydraulic tensioner is installed on the belt slack side of the alternator and a mechanical torsion spring tensioner is installed on the belt tight side of the alternator.
Representative of the art is U.S. Pat. No. 3,935,751 (1976) which discloses a stepless speed changing device and more particularly to the construction of an automatic speed changing device suitable for a vehicle or the like, the centrifugal force of said changing device is produced by the high-speed rotation of a rotating means which enables a plurality of claw blocks fitted pivotedly at a rotating disk to expand outward to increase the outside diameter thereof, and which, after the output of motive force, can produce automatically differential speed ratios of various magnitudes because of the change of said working outside diameters
What is needed is an expandable segmented pulley having an effective diameter that is variably determined according to an externally applied toque. The present invention meets this need.